My car blew out white smoke from exhaust. Mechanic says head gasket replacement

Get a second opinion in your area, but if they are going to rebuild the heads with the head gasket job it could be a little pricey. There is a lot of procedures and test that need to be done for BMW specs. Not sure the head would have to be rebuilt, but if the head is cracked then yes it could be pretty close on the price.

What fluid level(s) are effected? Is/ has your vehicle been overheating recently? Running hotter than normal? Today's car are complex as I'm sure your aware. So asking about price only can steer your in the wrong direction. What your vehicle mileage? Has your vehicle shown any signs prior to smoke from exhaust? On BMW's service technician MUST be aware of excessive crankcase or lower than specified values. We use a manometer to measure such critical data. Has your service technician indicated that it's related to Coolant consumption or engine oil consumption? I'm sorry that I your vehicle is showing some negative signs but more information is required in order to give you accurate feedback , best of wishes. Michael